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Full text of "Text Book Of Mechanical Engineering"

Appendix  VI.

1191

or E, F, arranged to provide the first and second speeds of
8 and 17 miles per hour; while the top speed of 25 miles is
obtained by a solid drive. First it must be understood that A
is locked to engine shaft: B and c are keyed to second shaft.
D is fixed to propeller shaft on which it runs freely, though
coupled to x by a hollow shaft: and E F slide on square
shafts. Thus for first or lowest speed E is slid into gear with F,
and the drive is A, B, and E, F; for th^ second speed E and F are
out of gear, but F is slid into clutch with D, thus driving as A, B :
c, D; and the third speed is procured by clutching F with A
directly. To reverse, a Marlborough wheel G is mounted on
eccentric bearings s, and the latter being rotated by lever R,
the drive is A B, EG, G F, which gives an opposite rotation at
slowest speed. The clutch lever p is disjointed, and re-united
by a strong spring Q, so the driver merely puts his lever ' hard
over/ and the wheel teeth find their places by the pressure of the
spring, a method less harmful to the teeth. The forks T T are
intermediately operated by bell cranks u and rod v, and the whole
is enclosed in casing L.

The propeller shaft is traced rearwards till it drives either a
chain shaft (p. 1004) or a 'live' hind axle // Fig. 1052, the
speed being further reduced by chain or bevels. The difficulty
of turning corners with a car of long wheel base is overcome by
compensation gear a. Imagine a drum a revolving freely on its
bearings, and carrying on diametral studs two bevel pinions which
gear respectively with two separate hind axles, one to each wheel
So long as the front wheels b b are steered ahead, the four bevels
rotate solidly and the hind road wheels revolve at equal rates;
but if the car be steered leftward, say, the hind wheel and bevel e
tend to remain stationary, when d would revolve at double the
speed of a, the smaller pinions serving as live rollers. In reality
the outer wheel merely travels more rapidly than the inner, in
automatically correct proportion (see p. 526). The portion of pro-
peller shaft between gear box and hind axle is made flexible by
universal joint m and telescopic coupling q, or by two universal
joints. The reduction bevels r and compensating gear s are
enclosed in a casing / which is cast with a bearing tube k on
which rest the springs *, and the wheel g is slipped upon a

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